This invention relates to the field of trenching and pipe-laying operations and, particularly, to an improved method and support and alignment apparatus for aligning a laser beam emitted from a laser beam generator thereby improving the efficiency of such trenching and pipe-laying operations.
In recent years, a collimated light beam emitted from a laser beam generator has found a great many uses, several of which are with regard to surveying applications and, particularly, as a reference line for the predetermined guidance of equipment for such things as tunneling, hydraulic pipe pressing, irrigation work, alignment of railroad tracks and other applications. In such uses, the laser beam may be either on a level, or horizontal, plane or inclined at a predetermined angle or grade from the horizontal.
In this regard, particular benefit has been achieved by incorporating the use of such laser beam references into such construction operations as trenching and pipeline setting which require a high degree of accuracy. Conventionally, pipe laying involved the use of crude surveying instruments and a great deal of human effort and time in order to properly position the pipes. Surveying operations were often complex and the chances of error were numerous.
The use of a laser beam projected parallel to and at a certain distance above the desired invert line of a sewer or other pipeline eliminates many of the inaccuracies inherent in such conventional techniques. One problem that remains significant, however, is the need to accurately align the laser beam and generator with a surface reference target positioned distant from the generator after it has been properly positioned directly above the point of origin for the construction. The dilemma centers around the fact that while the laser generator must be positioned below the surface of the ground in a construction hole or trench in order to provide the needed reference line for the trenching and pipe-laying operation, the initial alignment with the distant reference target must be made from above the ground. To resolve this problem, several prior art methods and apparata have been developed to accomplish this above-ground alignment of the subsurface laser generator:
______________________________________ Patent No. Inventor Issue Date ______________________________________ 3,279,070 Blount et al. 10/18/66 3,116,557 Trice 1/07/64 3,612,700 Nelson 10/12/71 3,879,132 Myeress 4/22/75 3,591,926 Trice 7/13/71 3,488,854 Trice 1/13/70 ______________________________________
It can be generally said that each of the above references requires some kind of separate above-ground sighting device which must be first aligned with the distant reference target and then used in some manner to hopefully orient the subsurface laser beam and generator in like alignment. Specifically, the system disclosed by the Trice references requires the employment of a transit and numerous incremental micrometer adjustments to establish the beam upon the true line and grade, as set forth in column 4 of the patent specification in U.S. Pat. No. 3,116,557 above. Blount also requires the use of a citing device 11 which is mechanically slaved to the light beam source housing in order to establish the beam on proper line and grade. Myeress discloses a similar apparatus, except that a lateral set off portion is used to enable the light beam generator to be mounted inside a particular section of pipe.
Nelson, on the other hand, provides a slight deviation from the other references by first surveying by conventional techniques to establish a reference line perpendicular to the desired line of construction and then pendulously suspending the laser beam generator with vertical and horizontal adjustments in the particular construction hole.
Other prior art variations can be seen in U.S. Pat. No. 3,911,589, also issued to Myeress, and in U.S. Pat. No. 3,997,267, issued to Met. The former discloses merely an adjustable support base for a field measurement device including a vertical adjustable rod with a laser generator attached thereto for vertically orienting the laser in a particular construction hole. The latter discloses a complex automatic leveling device for providing a reference line for surveying, pipe laying and related purposes in which the leveled beam is deflected to the desired angle relative to the horizontal regardless of the orientation of the entire instrument at any given time.
Once properly aligned, regardless of the method and apparatus used, the laser beam provides a reference both for the laying of pipe and for the prior digging operation using such machinery as a trencher or a backhoe. In this regard, the Nelson reference above suggests the use of a backhoe in combination with an opaque or translucent surface to interrupt the laser beam along the reference line to maintain the backhoe operation on a true course. Walsh, U.S. Pat. No. 3,708,232, further discloses a particular passive optical readout device for locating and positioning objects such as a backhoe with respect to a fixed laser beam established in space as a parametric guide line. In the Walsh device, when the laser beam impinges on any one of the ends of the plurality of fiber optic bundles in the input array, the corresponding output or readout end of that same fiber optic bundle will glow brightly in the readout array thereby indicating to the operator of the trenching machine that he is following the correct course.
With the pipeline trench properly dug, the pipe-laying operation can begin with the laser beam again providing the reference line for the positioning and laying of the individual sections of pipe. In this regard, much work has also been done concerning the development of target devices which may be positioned along the path of the laser beam to assure that each individual pipe is laid in the proper orientation with respect to the beam. Each of the following reference patents discloses a specific type of target device suitable for such a use.
______________________________________ Patent No. Inventor Issue Date ______________________________________ 3,907,435 Roodvoets 9/23/75 3,742,581 Roodvoeis 7/03/73 3,631,601 McNulty 1/04/72 3,599,336 Walsh 8/17/71 3,815,250 Roodvoets et al. 6/11/74 ______________________________________
Further work, as shown in U.S. Pat. No. 3,827,155, issued to Menzel, and in U.S. Pat. No. 3,827,156, issued to Roodvoets et al., has even been done with regard to a method and apparatus for blowing air through the pipeline during the laser beam alignment process in order to prevent gases from building up within the pipeline and thereby distorting the laser beam from its original path.
It will be appreciated from the foregoing that although much work has been done in the area of laser beam alignment and support for use in trenching and pipe-laying operations, many problems exist with such prior art methods and apparata. Specifically, the use of separate above-ground telescopes or other visual alignment devices which are mechanically or otherwise joined to their respective below-surface laser beam generators incorporates the possibility of many inaccuracies resulting from the particular extended connecting apparata. In addition, the alignment methods of the prior art are often exceedingly difficult and require numerous adjustments in order to hopefully establish the beam upon a true line and grade. In this regard, it is well known by contractors that a reduction in the beam set up and alignment time would allow their crews to accomplish more work per day thereby greatly increasing the efficiency of the trenching and pipe-laying operations.
Therefore, there has remained a need for an improved laser beam generator alignment and support method and apparatus which will simplify the alignment operation and eliminate the many steps required by prior art devices while also providing an efficient and accurate means for aligning the laser beam upon the desired line and grade.